Substrate for a display panel, and a display panel having the same

ABSTRACT

A substrate for a display panel includes an alignment accuracy measurement mark which is used for measuring alignment accuracy between patterns on the substrate without decreasing an aperture ratio of a pixel. The substrate for a display panel includes the alignment accuracy measurement mark in an isolated configuration which is used for measuring alignment accuracy between a pattern of a gate signal line and an auxiliary capacitance line and a pattern of a source signal line and a drain line, where the alignment accuracy measurement mark has a shape such that at least one straight line portion is included, is formed in a layer where the pattern of the source signal line and the drain line is formed, and is positioned on the gate signal line.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate for a display panel, and adisplay panel having the substrate, and specifically relates to asubstrate for a liquid crystal display panel which includes layersincluding patterns on a conductive film and an insulating film, and aliquid crystal display panel having the substrate.

2. Description of the Related Art

A common liquid crystal display panel includes an array substrate and acolor filter substrate, and a space therebetween is filled with a liquidcrystal. On surfaces of the array substrate and the color filtersubstrate, layers including patterns on a conductive film and aninsulating film are stacked.

FIG. 3 is a schematic plan view showing one example of patterns of lineswhich are formed on a conventional liquid crystal display panel 9, andthe lines for one pixel are shown. An array substrate includes a layerwhere a pattern of a gate signal line 912 and an auxiliary capacitanceline 915 is formed and a layer where a pattern of a source signal line913 and a drain line 914 is formed, and these layers are stacked via aninsulating film (not shown). By these patterns, thin film transistorsand predetermined lines are formed.

In order that the thin film transistor and the predetermined lines mayhave properties as designed, alignment of the pattern of the gate signalline 912 and the auxiliary capacitance line 915 with the pattern of thesource signal line 913 and the drain line 914 is required to beperformed with predetermined accuracy in forming the patterns. For thisreason, after the pattern of the gate signal line 912 and the auxiliarycapacitance line 915 and the pattern of the source signal line 913 andthe drain line 914 are formed, alignment accuracy between the patternsis measured. If the measured alignment accuracy is out of apredetermined permissible range, the source signal line 913 and thedrain line 914 are re-formed.

The measurement of the alignment accuracy is performed using imagerecognition. Accordingly, a mark or a line for measurement which is usedfor image recognition is sometimes formed in the source signal line 913and the drain line 914. For example, in FIG. 3, a linear section 914 aextending in an X-axis direction is formed in the drain line 914. Edgesof the linear section 914 a and edges of the gate signal line 912 aredetected using image recognition, and based on a result of thedetection, a positional relationship between the linear section 914 aand the gate signal line 912 in a Y-axis direction (e.g., a distance Dbetween a centerline C of the gate signal line 912 and a centerline B ofthe linear section 914 a of the drain line 914) is measured.

As a prior art literature relating to the present invention, JapanesePatent Application Unexamined Publication No. 2003-302654 is cited.

Incidentally, a liquid crystal panel is required to increase an apertureratio of each pixel in order to increase luminance. Accordingly, asshown in FIG. 3, in a case where structural elements 921 a to 921 earranged to control alignment of the liquid crystal are provided on acommon substrate, the drain line 914 is sometimes arranged to coincidewith one of the structural elements 921 a to 921 e as exact as possible.However, it is difficult to arrange the linear section 914 a extendingin the X-axis direction to coincide with the structural elements 921 ato 921 e, so that some sections of the drain line 914 do not coincidewith the structural elements 921 a to 921 e. As a result, the sectionswhich do not coincide with the structural elements 921 a to 921 e causea decrease in an aperture ratio of a pixel.

Therefore, it is preferable to decrease the area of the sections of thedrain line 914 which do not coincide with the structural elements 921 ato 921 e as much as possible in order to increase the aperture ratio.However, the linear section 914 a is required to have a certain lengthsuch that the edges of the linear section 914 a can be detected withpredetermined accuracy in image recognition. In addition, the widths ofthe sections of the drain line 914 which do not coincide with thestructural elements 921 a to 921 e cannot be narrowed because narrowingthe widths of the sections of the drain line 914 which do not coincidewith the structural elements 921 a to 921 e decreases a process marginfor the drain line 914, which may cause a reduction in yields.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a substrate for a display panel suchthat alignment accuracy measurement can be performed while improving anaperture ratio of a pixel and the improvement of the aperture ratio ofthe pixel is made without decreasing a process margin, and provide adisplay panel having the substrate.

According to a preferred embodiment of the present invention, asubstrate for a display panel includes a mark for alignment accuracymeasurement in an isolated configuration, which is used for measuringalignment accuracy between a first conductor pattern and a secondconductor pattern. Besides, “in an isolated configuration” means thatthe alignment accuracy measurement mark is not configured nor intendedto be electrically connected with a conductive element which forms thefirst conductor pattern or the second conductor pattern. In addition,the alignment accuracy measurement mark may be arranged not to have ornot to be intended to have an electrical or electronic function inrelation to the first conductor pattern or the second conductor pattern.

The alignment accuracy measurement mark is formed preferably in a layerwhere the first conductor pattern is formed or a layer where the secondconductor pattern is formed. The alignment accuracy measurement mark ispreferably placed at a position such that an aperture ratio of a pixelis not decreased by the alignment accuracy measurement mark. Forexample, when the alignment accuracy measurement mark is formed in thelayer where the second conductor pattern is formed, the alignmentaccuracy measurement mark is at least partially positioned on the firstconductor pattern.

It is preferable that the alignment accuracy measurement mark has ashape such that its position can be detected with accuracy when imagerecognition is made. For example, the alignment accuracy measurementmark is given a shape such that at least one straight line portion isincluded.

Besides, for the first conductor pattern, a pattern of a gate signalline is preferably used, and for the second conductor pattern, a patternof a source signal line and a drain line is preferably used.

According to various preferred embodiments of the present invention,alignment accuracy between the first conductor pattern (e.g., thepattern of the gate signal line) and the second conductor pattern (e.g.,the pattern of the source signal line and the drain line) can bemeasured using the alignment accuracy measurement mark in the isolatedconfiguration. As a result, the need to form the second conductorpattern so as to include a linear section for alignment accuracymeasurement is eliminated and the degree of design freedom for thesecond conductor pattern is increased, allowing the second conductorpattern to be designed so as to coincide with light shield elementsprovided on a common substrate as exact as possible, whereby theaperture ratio of the pixel can be improved.

In addition, the need to narrow the widths of the lines in the firstconductor pattern or the second conductor pattern in order to improvethe aperture ratio of the pixel is eliminated, so that the apertureratio of the pixel can be improved without decreasing a process margin.Further, by the improvement in the aperture ratio, a backlight isdecreased in cost.

If the alignment accuracy measurement mark is at least partiallypositioned on the first conductor pattern or the second conductorpattern, the alignment accuracy measurement mark does not decrease theaperture ratio of the pixel.

In addition, if the alignment accuracy measurement mark has a shape suchthat at least one straight line portion is included, the position of thealignment accuracy measurement mark can be detected with accuracy bydetecting an edge at the straight line portion using image recognition.

By including the above-described substrate, a display panel having ahigher aperture ratio of each pixel, and higher luminance can beobtained.

Other features, elements, processes, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of preferred embodiments of the presentinvention with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic plan view showing a configuration of a pixelformed on a substrate for a display panel according to a preferredembodiment of the present invention, and FIG. 1B is a cross-sectionalview showing the same along the line A-A of FIG. 1A.

FIG. 2 is a schematic plan view showing a configuration of a pixelformed on a substrate for a display panel according to another preferredembodiment of the present invention.

FIG. 3 is a schematic plan view showing a configuration of a pixelformed on a conventional substrate for a display panel.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A detailed description of a substrate for a display panel according topreferred embodiments of the present invention will now be given withreference to the accompanying drawings. In the following preferredembodiments, a case where an array substrate for a liquid crystaldisplay panel is used for the substrate for a display panel isdescribed.

FIG. 1A is a schematic plan view showing a configuration of a pixelformed on the substrate for a display panel according to a preferredembodiment of the present invention, and FIG. 1B is a cross-sectionalview showing the same along the line A-A of FIG. 1A. As shown in FIGS.1A and 1B, a substrate 1 for a display panel according to a preferredembodiment of the present invention includes a transparent substrate 16such as a glass substrate, a layer including a gate signal line 12 andan auxiliary capacitance line 15, a first insulating layer 17, a layerincluding a source signal line 13 and a drain line 14, and a secondinsulating layer 18, where the layer including the gate signal line 12and the auxiliary capacitance line 15, the first insulating layer 17,the layer including the source signal line 13 and the drain line 14, andthe second insulating layer 18 are stacked on a surface of thetransparent substrate 16. The source signal line 13 includes branchportions 13 a. In addition, the substrate 1 includes a mark 11 foralignment accuracy measurement in an isolated configuration, which ispositioned preferably on the gate signal line 12. Meanwhile, convexstructural elements 21 a to 21 e which are arranged to control alignmentof a liquid crystal are provided on a common substrate (e.g., a colorfilter substrate). Hereinafter, such structural elements are referred toas “alignment control structural elements”.

The gate signal line 12 and the auxiliary capacitance line 15 arepreferably made of the same material using the same process and formedin the same layer. On a surface of the layer, the insulating layer 17 isformed. Further, on a surface of the insulating layer 17, the sourcesignal line 13 and the drain line 14 made of the same material under thesame process are formed in the same layer. Thus, the layer including apattern of the gate signal line 12 and the auxiliary capacitance line15, and the layer including a pattern of the source signal line 13 andthe drain line 14 are stacked via the insulating layer 17. Forconfigurations, materials and formation methods of the gate signal line12, the auxiliary capacitance line 15, the source signal line 13 and thedrain line 14, conventional configurations, materials and formationmethods can be used, so that explanations thereof are omitted.

The alignment accuracy measurement mark 11 is used for measuring arelative position between the pattern of the source signal line 13 andthe drain line 14 and the pattern of the gate signal line 12. Thealignment accuracy measurement mark 11 is preferably made of the samematerial under the same process as the source signal line 13 and thedrain line 14 during the process of forming the source signal line 13and the drain line 14, and is preferably formed in the layer where thesource signal line 13 and the drain line 14 are formed. Accordingly, arelative positional relationship between the alignment accuracymeasurement mark 11, and the pattern of the source signal line 13 andthe drain line 14 is fixed.

The alignment accuracy measurement mark 11 is not configured norintended to be electrically connected with any of the gate signal line12, the auxiliary capacitance line 15, the source signal line 13 and thedrain line 14. In other words, the alignment accuracy measurement mark11 does not have or is not intended to have an electrical or electronicfunction in relation to the lines 12, 13, 14 and 15. More specifically,the alignment accuracy measurement mark 11 is not intended to have anycontribution to nor any influence on driving of a thin film transistor.

The alignment accuracy measurement mark 11 is arranged to have a shapesuch that an edge thereof can be detected using image recognition andthe position of the alignment accuracy measurement mark 11 can becalculated based on the detected edge. For example, the shape of thealignment accuracy measurement mark 11 preferably is a quadrilateralsuch as a square as shown in FIG. 1A and a rectangle. When the alignmentaccuracy measurement mark 11 has a shape such that opposed sides areincluded, e.g., a quadrilateral, edges at the opposed sides are detectedand a centerline thereof can be accordingly calculated, allowingposition measurement of the alignment accuracy measurement mark 11 withhigh accuracy.

The shape of the alignment accuracy measurement mark 11 is not limitedto a quadrilateral, and the alignment accuracy measurement mark 11 mayhave a shape such that at least one straight line portion is included.In this case, it is preferable that the straight line portion of thealignment accuracy measurement mark 11 is arranged to extend in anX-axis direction when the alignment accuracy measurement mark 11 isintended for alignment accuracy measurement in a Y-axis direction.Meanwhile, it is preferable that the straight line portion of thealignment accuracy measurement mark 11 is arranged to extend in theY-axis direction when the alignment accuracy measurement mark 11 isintended for alignment accuracy measurement in the X-axis direction.When the alignment accuracy measurement mark 11 has such a shape, theposition thereof in the intended axis direction can be measured bydetecting an edge at the straight line portion.

Next, a manner of alignment accuracy measurement between the pattern ofthe source signal line 13 and the drain line 14 and the pattern of thegate signal line 12 using the alignment accuracy measurement mark 11will be described. The description is given to the case of the alignmentaccuracy measurement in the Y-axis direction.

After the gate signal line 12 and the auxiliary capacitance line 15, thefirst insulating layer 17, the source signal line 13 and the drain line14, the alignment accuracy measurement mark 11, and the secondinsulating layer 18 are formed on the transparent substrate 16, a regionincluding the alignment accuracy measurement mark 11 is photographed.Here, the edges of the gate signal line 12 on which the alignmentaccuracy measurement mark 11 is positioned are brought into view. Then,the edges of the alignment accuracy measurement mark 11 which areparallel to the X-axis direction, and the edges of the gate signal line12 which are parallel to the X-axis direction are detected using imagerecognition. Based on the detected edges, the position of a centerlineof the alignment accuracy measurement mark 11 and the position of acenterline of the gate signal line 12 are calculated (in FIGS. 1A and1B, a state where the centerline of the alignment accuracy measurementmark 11 coincides with the centerline of the gate signal line 12 isshown, and the line A-A indicates a centerline common to both of thecenterlines in such a state). Then, based on the calculated centerlines,a relative positional relationship in the Y-axis direction between thealignment accuracy measurement mark 11 and the gate signal line 12 iscalculated. Accordingly, the alignment accuracy measurement in theY-axis direction between the pattern of the gate signal line 12 and thepattern of the source signal line 13 and the drain line 14 can beperformed.

If the calculated relative positional relationship falls within apermissible range, the next process is started. If the relativepositional relationship is out of the permissible range, the sourcesignal line 13 and the drain line 14 are re-formed. Besides, for amethod of image recognition and an apparatus for image recognition, avariety of conventional methods and apparatuses can be used, so thatexplanations thereof are omitted.

Arranging the alignment accuracy measurement to be performed using thealignment accuracy measurement mark 11 as described above eliminates anecessity to form the drain line 14 so as to have a linear section foralignment accuracy measurement, so that the degree of design freedom forthe drain line 14 increases, allowing the drain line 14 to be designedso as to coincide substantially over the entire length with any one ofthe alignment control structural elements 21 a to 21 e of the commonsubstrate, whereby an aperture ratio of an pixel can be improved. Inaddition, a necessity to narrow the width of the drain line 14 in ordernot to decrease the aperture ratio of the pixel is eliminated, so that aprocess margin does not have to be decreased. Further, the alignmentaccuracy measurement mark 11 does not decrease the aperture ratio of thepixel because it is positioned on the gate signal line 12. In addition,the alignment accuracy measurement mark 11 has no influence on drivingof the pixel because it is in the isolated configuration.

While a preferred embodiment of the present invention has been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention.

In the above-described preferred embodiment of the present invention,the case where the shape of the alignment accuracy measurement mark 11preferably is a square is described. However, the shape of the alignmentaccuracy measurement mark 11 is not limited to a square. It is essentialonly for the alignment accuracy measurement mark 11 to have a shape suchthat the edges thereof can be detected using image recognition and theposition of the alignment accuracy measurement mark 11 can be calculatedbased on the detected edges.

FIG. 2 is a view of a modified example of the substrate for a displaypanel according to the above-described preferred embodiment of thepresent invention. As shown in FIG. 2, an alignment accuracy measurementmark 11′ preferably has the shape of a rectangle. When the alignmentaccuracy measurement mark 11′ is used for alignment accuracy measurementin the Y-axis direction, the edges of the alignment accuracy measurementmark 11′ which are parallel to the X-axis direction are arranged to havelengths such that they can be detected with predetermined accuracy usingimage recognition. Meanwhile, the lengths of the edges of the alignmentaccuracy measurement mark 11′ which are parallel to the Y-axis directionare not specifically limited. Accordingly, it is also preferable thatthe alignment accuracy measurement mark 11′ has the shape of a rectanglewhich is long in the Y-direction other than a rectangle which is long inthe X-direction as shown in FIG. 2.

It is also preferable that the alignment accuracy measurement mark hasthe shape of a triangle or other polygons. In addition to the shapeshaving a straight line portion included therein, it is preferable thatthe alignment accuracy measurement mark has a shape such that a curvedline portion is included. For example, if the alignment accuracymeasurement mark has a shape such that a segment of a circle isincluded, the center of the segment of the circle can be calculatedbased on an edge detected at the segment. Accordingly, it is alsopreferable that the alignment accuracy measurement mark has the shape ofa circle, a semicircle, or a sector.

It is essential only for the alignment accuracy measurement mark to beplaced at a position such that a relative positional relationship withthe gate signal line can be measured. For example, in a case where thegate signal line and the auxiliary capacitance line are simultaneouslyformed (in other words, a relative positional relationship between thegate signal line and the auxiliary capacitance line is fixed) as in thepreferred embodiments of the present invention, it is also preferablethat the alignment accuracy measurement mark is positioned on theauxiliary capacitance line. The alignment accuracy measurement mark isnot necessarily required to be positioned on the gate signal line or theauxiliary capacitance line. For example, it is also preferable that thealignment accuracy measurement mark is positioned in the vicinity of thegate signal line or the auxiliary capacitance line. However, in ordernot to decrease the aperture ratio of the pixel, the alignment accuracymeasurement mark is preferably placed out of the region of the pixel.

The alignment accuracy measurement mark is not necessarily required tobe formed in the layer where the source signal line and the drain lineare formed. In addition, although the alignment accuracy measurementmark is entirely positioned on the gate signal line in theabove-described preferred embodiments of the present invention, it isnot limited to being positioned as such and is preferably partiallypositioned on the gate signal line.

Incidentally, the description has been given to the case where thealignment accuracy measurement mark is used for the alignment accuracymeasurement in the Y-axis direction in the above-described preferredembodiments of the present invention. However, it is also preferablethat the alignment accuracy measurement mark is used for the alignmentaccuracy measurement in the X-axis direction.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing the scope andspirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

1. A substrate for a display panel comprising: a first layer including a first conductor pattern defining a gate signal line; a second layer including a second conductor pattern defining a source signal line; an insulating layer arranged such that the first layer and the second layer are stacked with the insulating layer disposed therebetween on a surface of the substrate; and an isolated pattern portion; wherein the source signal line includes at least one branch portion that extends away from the source signal line in at least one direction in which the gate signal line extends; the isolated pattern portion is spaced from the at least one branch portion of the source signal line. 